This invention relates generally to fans for moving air. More particularly, the invention relates to an improved inlet orifice structure and centrifugal flow fan impeller assembly.
Centrifugal flow fans and their associated inlet orifices are widely used in a number of applications in the field of heating, ventilation and air conditioning (HVAC). Important objectives in the design and manufacture of HVAC systems and components are to minimize size, optimize air flow rates and minimize radiated noise.
In operation, air enters a centrifugal flow fan generally along the fan's axis of rotation, undergoes a change of flow direction within the fan and exits the fan radially. Depending on the application, the air may discharge through 360 degrees around the fan or a scroll with one or more outlets may surround the fan impeller to direct the discharge air in one or more specific directions. In HVAC applications, an electric motor usually drives the fan impeller. Stationary inlet orifices guide the incoming air into the fan suction.
To achieve size and performance objectives, it is important to minimize nonuniform flow and flow separation as the air flows through the fan.